The invention relates to turbine engine stator walls provided with abradable coatings, and in particular for use in aeroengines, such as fan retention casings or low-pressure compressor casings.
Such a casing may be made up of a plurality of touching wall sectors that together surround rotary blades driven in rotation by combustion gas. It is also possible for the wall to comprise a closed structure or to be made up of two half-shells. In order to ensure that operation takes place with little clearance, and thus in order to ensure that the turbine engine provides the requested performance in terms of consumption and efficiency, the rotary blades need to come into contact with abradable coatings arranged on the casing. Typically, an abradable coating is constituted by a material based on a resin filled with a pore-generating agent of the type comprising hollow microbeads made of refractory material, and the coating is usually formed by molding or by physical deposition, e.g. by thermal spraying, onto the surface that is to be protected.
Unfortunately, depending on the nature of the structural portion, i.e. depending on whether it is made of metal or of composite material, it can be found that the abradable material can lose adhesion, causing it to become separated and thus to greater or smaller quantities of the material constituting the coating being ingested by the bypass stream of the turbine engine.
In order to solve this problem of loss of adhesion, it is known to sand or grind the structural portion prior to depositing the thermal protection. Unfortunately, that solution cannot be generalized to surfaces that have received electrolytic or electrochemical treatment for protection or passivation purposes, since such an operation has the consequence of destroying that particular treatment.